content: package lambda2sql;
  
  import com.trigersoft.jaque.expression.*;
  
  import java.util.ArrayList;
  import java.util.List;
  
  import static com.trigersoft.jaque.expression.ExpressionType.*;
  
  public class ToSqlVisitor implements ExpressionVisitor<StringBuilder> {
  
  	private StringBuilder sb = new StringBuilder();
  	private Expression body;
  	private List<ConstantExpression> parameters = new ArrayList<>();
  
  	private static String toSqlOp(int expressionType) {
  		switch (expressionType) {
  			case Equal:
  				return "=";
  			case LogicalAnd:
  				return "AND";
  			case LogicalOr:
  				return "OR";
  			case Convert:
  				return "";
  		}
  		return ExpressionType.toString(expressionType);
  	}
  
  	@Override
  	public StringBuilder visit(BinaryExpression e) {
  		boolean quote = e != body && e.getExpressionType() == LogicalOr;
  
  		if (quote) sb.append('(');
  
  		e.getFirst().accept(this);
  		sb.append(' ').append(toSqlOp(e.getExpressionType())).append(' ');
  		e.getSecond().accept(this);
  
  		if (quote) sb.append(')');
  
  		return sb;
  	}
  
  	@Override
  	public StringBuilder visit(ConstantExpression e) {
  		if (e.getValue() instanceof String) {
  			return sb.append("'").append(e.getValue().toString()).append("'");
  		}
  		return sb.append(e.getValue().toString());
  	}
  
  	@Override
  	public StringBuilder visit(InvocationExpression e) {
  		e.getArguments().stream().filter(x -> x instanceof ConstantExpression).forEach(x -> parameters.add((ConstantExpression) x));
  		return e.getTarget().accept(this);
  	}
  
  	@Override
  	public StringBuilder visit(LambdaExpression<?> e) {
  		this.body = e.getBody();
  		return body.accept(this);
  	}
  
  	@Override
  	public StringBuilder visit(MemberExpression e) {
  		String name = e.getMember().getName();
  		name = name.replaceAll("^(get)", "");
  		name = name.substring(0, 1).toLowerCase() + name.substring(1);
  		return sb.append(name);
  	}
  
  	@Override
  	public StringBuilder visit(ParameterExpression e) {
  		parameters.get(e.getIndex()).accept(this);
  		return sb;
  	}
  
  	@Override
  	public StringBuilder visit(UnaryExpression e) {
  		sb.append(toSqlOp(e.getExpressionType()));
  		return e.getFirst().accept(this);
  	}
  
  }